The present invention is directed to a method and device for measuring characteristics of an optical pickup or optical disc. The present invention incorporates a recording and/or reproducing system of optical disc.
It is currently known that there has been an inspection device for characteristic of optical pickup, which has been used for optical disc drive. The inspection device for characteristic of optical pickup, for example, is used for shipping inspection (inspection of optical pickup before shipping) or accepting inspection (inspection of optical pickup prior to accepting) of optical pickup, etc. It inspects whether optical pickup satisfies prescribed specifications.
FIG. 3 shows a block configuration of a known inspection device for characteristic of optical pickup. The inspection device for characteristic of optical pickup 100, shown in the FIG. 3, includes the following: optical pickup 101, which will be an inspection object; test bench 102, where optical disc will be set; matrix circuit 103, to which the output from a photo detector possessed by optical pickup 101, will be provided, and which will output reforming (RF) signals; and servo control circuit 104, which will servo control for the reproducing drive of optical disc, based on the output from the matrix circuit 103.
In addition, the inspection device for characteristic of optical pickup 100, also has the following: measuring circuits 105a-105n, each of which will measure the various values of characteristics of optical pickup, based on the output from the matrix circuit 103; multiplexer 106, which will switch the output from the measuring circuits 105a-105n; analog/digital converting circuit 107, which will convert the output from one of the circuits, which has been converted by internal multiplexer 106 of each measuring circuit 105a-105n, into digital data; and computer 108, which will perform statistical application on the output data from the analog/digital converting circuit 107, and will display the results.
Optical pickup 101 is an inspection object for the inspection device for characteristic of optical pickup 100. This optical pickup 101 can, for example, be installed to the inspection device for characteristic of optical pickup 100, and be freely attached or removed.
The optical pickup 101 also has laser diode, beam splitter, object lens, and photo detector, etc. Furthermore, the optical pickup 101 lets laser emitted from laser diode gather on the optical disc through beam splitter, object lens, etc. Then, the optical pickup 101 lets reflected light from an image on photo detector. The photo detector possessed by the optical pickup 101, is photoelectric conversion element; it converts the reflected light which has formed an image, into electric signals.
In general, the optical pickup 101 has multiple photo detectors: for example, it has a photo detector divided into a quarter in cross-shape; and it also has another photo detector for detecting side spot at both sides of the above photo detector divided into a quarter in cross-shape. The output from such photo detectors will be provided to the matrix circuit 103.
The test bench 102, where optical disc will be set, rotates and drives the optical disc in order to reform the optical disc. In addition, the optical disc which will be set in the test bench 102, is used as a reference for the inspection device for characteristic of optical pickup 100.
The matrix circuit 103, to which the output from each photo detector possessed by the said optical pickup 101 will be provided, generates reforming (RF) signals, focus error (FE) signals, and tracking error (TE) signals, etc. from the output from such photo detectors.
For example, if photo detectors possessed by the optical pickup 101 consist of the one divided into a quarter in cross-shape and the one used for side spot, the matrix circuit 103 will detect each signal as follows: the matrix circuit 103 processes the total sum of each output, based on the output from the photo detector divided into a quarter, then outputs the result of processing as RF signals. The matrix circuit 103 processes the sums of the output from two (2) photo detectors which are an object at the center of a cross-shape, and processes the difference between these sums, then outputs the result of processing as FE signals. Therefore, the matrix circuit 103 outputs FE signals, by using the astigmatism or astigmatic method. In addition, the matrix circuit 103 processes the difference between the outputs, based on the output from the photo detector used for side spot, then outputs the result of processing as TE signals.
The matrix circuit 103 provides RF signals, FE signals, and TE signals, which are processed as the above mentioned, to servo control circuit 104 and measuring circuits 105a-105n. 
The servo control circuit 104 servo-controls as reproducing drive of optical disc, based on the RF signals, FE signals, and TE signals. More specifically, the servo control circuit 104 performs focus servo control, tracking servo control, thread servo control, and tilt servo control.
The measuring circuits 105a-105n operate the characteristics value of the optical pickup 110. Each measuring circuits 105a-105n measures different characteristics values. Therefore, the inspection device for characteristic of optical pickup 100 is equipped with the number of measuring circuits 105a-105n, which are equivalent to the number of the characteristics values to be measured.
Furthermore, each measuring circuits 105a-105n performs filtering processing by analog processing, peak detecting processing, and frequency/voltage conversion processing, and measures characteristics values. The first measuring circuits 105a, for example, measures the level of signals with xe2x80x9cSxe2x80x9d shaped curve during leading-in of a focus servo loop, based on FE signals. The second measuring circuits 105b, for example, measures the level of TE signal, based on the TE signals. The third measuring circuits 105c, for example, measures the level of RF signal, based on the RF signals. Finally, the forth measuring circuits 105d, for example, measures the jitter component of RF signal, based on the RF signals.
Multiplexer 106 switches the output from each measuring circuits 105a-105n, then supplies the output from either of the measuring circuits to the analog/digital converting circuit 107.
The analog/digital converting circuit 107 converts the output from each measuring circuit 105a-105n, which has been provided through the multiplexer 106, into digital data, then supplies it to the computer 108. The conversion speed of the analog/digital converting circuit 107 is slow, because the output from each measuring circuit 105a-105n is almost at DC level. For example, the conversion speed of the analog/digital converting circuit 107 is about 1 KHz.
The computer 108 performs statistical application on digital data supplied from the analog/digital converting circuit 107, then displays the results.
As we have discussed in the above sections, the current inspection device for characteristic of optical pickup 100 measures the characteristics value of the optical pickup 101, by using the measuring circuits 105a-105n which are equipped to be the same number of the characteristics values to be measured, then displays the results to users, by using the computer 108.
However, the current inspection device for characteristic of optical pickup 100 has measured the characteristics value of the optical pickup 101, by using the multiple measuring circuits 105a-105n through analog processing. Therefore, the current inspection device for characteristic of optical pickup 100 has had a problem that stable characteristics value cannot be obtained, because some effect is generated by uneven characteristics or elapsed change of each measuring circuit 105a-105n. Furthermore, there has been another problem in the current inspection device for characteristic of optical pickup 100: when measuring items of characteristics values should be added or measuring items of characteristics values should be amended, addition or amendment of circuits, in terms of hardware, is necessary for the measuring circuit 105a-105n. This increases cost and needs longer time.
In addition, the current inspection device for characteristic of optical pickup 100 has measured characteristics values based on RF signals, FE signals, or TE signals, which are supplied from the matrix circuit 103. Therefore, the current inspection device for characteristic of optical pickup 100 has had a problem that error caused by temperature characteristics or elapsed change of the matrix circuit 103 influences on the characteristics value to be measured.
Moreover, the current inspection device for characteristic of optical pickup 100 has measured each characteristics value, by using the multiple measuring circuits 105a-105n through analog processing, or has measured characteristics values, based on RF signals, FE signals, or TE signals, which are supplied from the matrix circuit 103. This causes a problem for a system which uses multiple number of the inspection device for characteristic of optical pickup 100: the results of measurement by each device vary, and it is difficult to correct such unevenness.
According to the present invention, there is provided a device for measuring characteristics of an optical pickup comprising a reproducing drive and a photoelectric conversion section, wherein the device comprises:
servo control means for controlling the reproducing drive;
analog to digital conversion means for converting analog data output from the photoelectric conversion section to a digital data output;
storage means for storing digital data output from the analog to digital conversion means; and
processing means for determining characteristics of the optical pickup based upon the digital data stored in the storage means.
The analog to digital conversion means may sample the output from the photoelectric conversion section at a frequency of 50 kHz or greater.
The photoelectric conversion section may comprise a plurality of outputs; and the analog to digital conversion means may simultaneously sample the plurality of outputs of the photoelectric conversion section.
The analog to digital conversion means may further comprise a plurality of sample hold circuits.
The plurality of sample hold circuits may simultaneously sample the plurality of outputs of the photoelectric conversion section to produce a digital data output.
The processing means may perform an adjustment to the servo control means in accordance with the characteristics of the optical pickup.
The processing means may determine the characteristics of the optical pickup after each the adjustment of the servo control means.
The processing means may adjust the tracking balance, tracking bias or defocus of the servo control means in accordance with the characteristics of the optical pickup.
The optical pickup may comprise an optical disk.
According to another aspect of the invention, there is provided a method of measuring characteristics of an optical pickup comprising a reproducing drive and a photoelectric conversion section, wherein the method comprises the steps of:
sampling a plurality of outputs from the photoelectric conversion section to produce sample data;
converting the sample data into digital data;
storing the digital data in a storage device;
processing the digital data stored in the storage device to determine characteristic of the optical drive; and
adjusting a servo control means to control the reproducing drive in accordance with the characteristic of the optical drive.
The step of sampling a plurality of outputs from the photoelectric conversion section may be preformed at a frequency of 50 KHz or greater.
The sampling step may further comprise simultaneously sampling the plurality of outputs from the photoelectric conversion section to produce sample data.
The sampling step may further comprise simultaneously sampling the plurality of outputs from the photoelectric conversion section to produce sample data using a plurality of analog to digital conversion circuits.
The sampling step and converting step may be performed by a plurality of sample hold circuits.
The adjusting step may further comprise adjusting tracking balance, tracking bias or defocus of the servo control means.
The processing step may be repeated after the adjusting step.
According to a further aspect of the invention, there is provided an optical disk recording/reproducing system comprising:
reproducing drive for rotating an optical disk at a predetermined rate;
optical pickup comprising a plurality of photoelectric conversion sections;
servo control means for controlling the reproducing drive based upon an output signal from the plurality of photoelectric conversion sections;
analog to digital conversion means for converting the output from the photoelectric conversion sections into digital data;
storage means for storing the digital data;
processing means to determine characteristics of the optical pickup based upon the digital data stored in the storage means; and
the processing means further comprises means for controlling the servo controller means based upon the digital data stored in the storage means.